Now, let me start by explaining how Catwoman works in Arkham City. The following comes from Kotaku.com
One of the teased elements of Rocksteady's Batman: Arkham City is the ability to play as the caped crusader's frenemy/love interest/ally Selina Kyle, aka the Catwoman. It wasn't clear what her involvement would be in the main storyline, other than that she would be a part of it.
But last week, when I set up the retail version of the game, I found that I had to enter a second code for a sizable download, which promised to "unlock Catwoman as a playable character in the game." As was confirmed by WBIE yesterday, codes for the Catwoman content are given out with new copies of the game, but held back from used purchasers until they pay $10 to get it via a "VIP Pass".
(NOTE: We're already seeing signs that there are loopholes to getting this Catwoman DLC. Retailer GameStop is giving these codes out for free to people who buy the game used, according to a leaked memo from the retail chain, removing the requirement to get the game new to play as Catwoman. Whether you're angling for a freebie code that way or simply planning to buy the game new to get your code inside the game box, take heed of what the content actually is. On with the description...)
The Catwoman content is substantial. It includes an entirely different beginning to the game, as well as four large-ish gameplay chapters throughout the story. Each one is about fifteen or twenty minutes, with a mix of exploration, stealth, and combat, all of it unique. There's a ton more content if you choose to really explore or mess about, especially considering that there are a whole bunch of red riddler trophies that only Catwoman can collect. The content is also not included on the disc—it's downloadable, so before you play, be ready to enter a code and wait for a 253MB download to complete.
Catwoman is playable through the game's open map, and has her own unique gadgets and some fun methods for traversing the rooftops of Arkham.
Combat is fun and fast, a surprisingly different feel from combat as the Dark Knight. Catwoman has her own page of upgrades and her own gadgets, though there are only a few of them. Furthermore, she has a questline involving at least one major Batman character that doesn't appear in the main Arkham City storyline at all.
Catwoman is also playable in the game's unlockable Riddler challenge rooms, which adds a new way to play the already deep and enjoyable challenges. She has three different appearances, which I've captured and put together in an image.
The best thing about playing Catwoman is setting her sprinting, leaping, and swinging about the open map. At first I wasn't sure about it, since she isn't, y'know, Batman. But once I got the hang of it, I found that there is a crazed quality to her that Batman lacks, and it's really fun. She doesn't have the Dark Knight's grappling hook, using her whip to swing from building to building, and as a result players must sprint up to the edges of buildings and swan-dive off, catching purchase with her whip in midair. It's exhilarating and enjoyable.
It's all very good stuff, and without it the game would feel incomplete. Considering that you'll be purchasing a "pass" in place of the content itself, it sounds as though your $10 might get you more than just the one character. I could imagine other playable characters and even mini-storylines released through the pass, possibly even at no extra charge. But that's just speculation.
Catwoman's missions are a substantial chunk of gameplay, a welcome change of pace and a fun side story. If you're buying the game used, you'll have to take the cost of the online pass into account if you want to play them. And if you're planning to play Arkham City from somewhere without an internet connection, you'll miss out entirely.
For legality, a scan from Uncanny X-Force #16